In 1966 I went to Leeds University to study Electrical and Electronic Engineering. At an introductory lecture from the Professor, we were told we would need a slide rule for the course. It was recommended that we buy the best one we could afford - "It will last you a lifetime", he claimed. Following the advice, I went to the student stationery shop and bought the best I could afford, a Faber Castell. This instrument could multiply, divide, perform trigonometric calculations, raise numbers to any power and even calculate decimal roots.
But, by 1970 I was using desk top calculators and in about 1972 I bought my first pocket calculator, vastly outperforming the slide rule for multiplying and dividing (although trigonometry, powers and roots came later). The slide rule died virtually overnight. In use by mathematicians, scientists and engineers for over 250 years, it was so suddenly overtaken by the electronic calculator. But, prior to 1970, most feats of engineering were accomplished using a slide rule.
I still keep a slide rule on my desk at work. Not only is it a conversation piece, new graduates find it a powerful challenge to discover how to use it and, particularly, why it works